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When summertime finally arrives in Portland, many of us can’t get enough sun after enduring months of drizzly, overcast weather.

Maybe we should be careful what we wish for.

Scientists warn that global warming will bring longer and more intense heat waves — even in temperate climes like Portland’s — and those may put vulnerable seniors, children and people with respiratory illnesses at risk.

“More people die from heat-related illnesses in the world than all other natural disasters combined,” says Vivek Shandas, associate professor at Portland State University’s College of Urban and Public Affairs.

In 1995, a scorching Chicago heat wave led directly to 739 deaths.

More than 14,800 French people died in a brutal 2003 heat wave.

Closer to home, more than 600 Californians died in a 2006 heat wave.

Portland has been spared such calamities, but a 2009 heat wave here ranked as the hottest in the Northwest since record-keeping began in 1901, says Kathie Dello, deputy director of the Oregon Climate Service at Oregon State University.

“We are paying attention to heat waves in this part of the country,” Dello says, “even though people don’t think Portland is a hot place.” In some ways we’re more at risk, she says, because most Portland-area residences lack air conditioning.

Pacific Northwest temperatures have climbed an average of 1.5 degrees Fahrenheit since 1920, according to a 2009 report by the Climate Impacts Group at the University of Washington.Â

The Intergovernmental Panel on Climate Change projects that average global temperatures will rise up to 1.2 degrees Fahrenheit by 2030, 3.1 degrees by mid-century and up to 5.5 degrees by late-century. Â

Large swaths of Portland will get even hotter because of the urban heat island effect, essentially hot spots in the terrain associated with masses of concrete and asphalt and a lack of tree canopy. Â

Shandas, trying to apply lessons from the Chicago and Paris heat waves, is using maps generated by fellow PSUÂ researcher David Sailor that document where those urban heat islands occur in Portland, to pinpoint populations at greater risk during heat waves, down to the neighborhood level.

In Chicago, he says, there were many casualties among seniors living in upper floors of apartment buildings, where rising heat exposed them to greater temperatures. Â

“People living in high-rises literally cook,” Shandas says. Some bodies were 130 degrees when they were found dead in their Chicago apartments. Many seniors in the Chicago heat wave were afraid to leave their apartments or even open windows.

Portland doesn’t have the towering public housing projects of Chicago. But it does have a large population of low-income and senior residents in public housing or downtown single-room-occupancy hotels that lack air conditioning. And downtown Portland is one large urban heat island.

Portland also is a magnet for senior citizens relocating to live near children and grandchildren. Like much of the country, we’re projected to have an ever-increasing share of residents older than 85 — the population most susceptible to heat stroke, dehydration and respiratory problems exacerbated by extreme heat.

Mapping the heat

Sailor’s urban heat island maps of the Portland area show some parts of the metro area are around 10 degrees warmer than other areas. The warmest pockets tend to be where there is lots of roadway, parking lots and warehouses, and relatively few trees. Those include downtown, the inner east side of Portland, the Northwest industrial district, the airport and surrounding Columbia Corridor, along freeways and busy arterials such as 82nd Avenue, Sandy Boulevard, Foster Road and Killingsworth Street.Â

On a hot summer day, exposed urban roofs, road surfaces and pavements can soar 50 to 90 degrees hotter than the air, according to the Environmental Protection Agency. By nightfall, urban heat islands in some large U.S. cities can still be 22 degrees warmer than other areas, the EPA says.

Shandas and his colleagues examined urban heat islands in 15 metropolitan areas around the country. They found the effect was greater in Phoenix, Houston and Atlanta, but that Portland ranked in the middle of the pack, similar to the heat island impacts in Minneapolis, Denver and Orlando.

On the first day of a heat wave, concrete and asphalt tend to absorb and store much of the heat. “The next day the sun comes up and it warms up even more,” Shandas says.

There’s no official temperature that defines a heat wave, Dello says, but most agree it’s a series of at least three days of stifling heat. That’s also the point when people’s health starts to get imperiled.

Hot summer days in the city often are associated with more incidences of road rage, traffic accidents, hospital admissions and drownings. Urban heat islands bring additional impacts, according to the EPA: greater air pollution and greenhouse gas emissions, hampered water quality, and heat-related illness and mortality.

Shandas and his colleagues aren’t the only local researchers using the urban heat island maps. Multnomah County procured a Centers for Disease Control grant to study the potential health impacts of a warming climate. Among other endeavors, researchers are seeking records of emergency hospital admissions for people with asthma, to correlate their residences with the urban heat island maps. County researchers also will evaluate the potential for increases in Dengue fever and other diseases more prevalent in hotter areas, says Julie Sullivan-Springhetti, county spokeswoman. The county’s Office of Emergency Management is using the maps to track where vulnerable people live, such as those in more than 600 adult foster care homes, says Paul Iarrobino, program supervisor for Multnomah County Aging and Disability Services.

Minimizing heat islands

There are many things communities can do to shrink the impact of heat islands, and many are under way in Portland.

The city Bureau of Environmental Services is promoting bioswales along many streets, which also reduce the need to treat storm water in the sewage treatment plant. The bureau also offers subsidies so homeowners can install green roofs, vegetated materials that reduce urban heat and make roofs last longer.

There also are widespread volunteer campaigns to plant more street trees and convert unneeded concrete into gardens.

On the web, Multnomah County now posts a list of locales where people can get relief on punishing hot days, including air- conditioned malls and libraries. In collaboration with senior services groups, the county has designated four “cooling centers,” which offer people organized activities and relief from the heat. Those are activated when it appears there will be three days in a row at more than 95 degrees, Iarrobino says.

During heat waves, there are contingency plans for people to check in on shut-ins who receive meals from Loaves and Fishes, he says. Many solutions are simple but can save lives, Shandas says, such as getting to know elderly neighbors down the block, and checking in with them during heat waves.